Valve drive for an internal combustion engine

ABSTRACT

A valve drive is suited for an internal combustion engine that has a camshaft with a sliding cam device. The sliding cam device is equipped with cam paths lying next to each other with different cam forms and hoisting curves which function together with actuation elements equipped with control pins for the adjustment of the sliding cam device. For optimization of the valve track, at least one hoisting curve of the sliding cam device carrying the cam paths is equipped with different hoisting curve sections for the engagement of the control pin of the corresponding actuation element.

This application claims the priority of German application 103 32 927.7,filed Jul. 19, 2003, the disclosure of which is expressly incorporatedby reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention concerns a valve drive for an internal combustionengine including a camshaft, and a sliding cam device equipped with campaths lying next to each other with different cam forms and hoistingcurves which function together with actuation elements equipped withcontrol pins for adjustment of the sliding cam device.

A valve drive for an internal combustion engine known from Europeanpublication EP 0 798 451 B1 comprises a camshaft with a sliding camdevice. The sleeve-type sliding cam device located on the camshaft isequipped with hoisting curves at a distance and cam paths lying next toeach other with different cam forms. The hoisting curves work togetherwith actuation elements equipped with control pins for the adjustment ofthe sliding cam device. This valve drive offers important capabilitiesin order to realize a highly effective variable valve control withcomparably simple means with the goal to improve its performance andconsumption.

It is one object of this invention to design a valve drive of this typein such a way that the sliding cam device forms a model construction andswitch functions of the different cam paths that are executed via thecontrol pins by actuation elements and a hoisting curve can be performedquickly, safely and exactly.

This object is achieved according to the invention through providing atleast one of the hoisting curves of the sliding cam device equipped withthe cam paths with different hoisting curve sections for an engagedcontrol pin of a corresponding actuation element. Additionalcharacteristics further developing the invention are specified independent claims.

Advantages achieved by this invention include assurance, thanks to thesliding cam device with the hoisting curves having various hoistingcurve sections, of a smooth and, therefore, functionally optimaladjustment course of the sliding cam device for the switching ofdifferent cam paths. Here the different hoisting curve sections can berepresented without any difficulties in the hoisting curves. The slidingcam device with ring elements is a component that can be manufactured byreasonable means, whereby the ring can easily be incorporated into thehoisting curves.

Finally, it is possible to manufacture a sliding cam hub of the slidingcam device and the ring elements in one piece, although assembling thesliding cam hub and the ring elements from several parts is alsoconceivable.

An embodiment of the invention is shown in the drawings and is describedin greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an inclined view of a valve drive of an internal combustionengine according to the invention with a slide cam device,

FIG. 2 illustrates a longitudinal section through the sliding cam deviceof FIG. 1,

FIG. 3 illustrates a section along line III-III of FIG. 2,

FIG. 4 illustrates hoisting curves of the sliding cam device, and

FIG. 5 illustrates a schematic detail X of FIG. 4 on a larger scale.

DETAILED DESCRIPTION OF THE INVENTION

Only the valve drive 2 with inlet valves 3 and 4 and outlet valves 5 and6 (four-valve technology) are represented of an internal combustionengine 1 suited for installation into a motor vehicle, which valves areeach located above the combustion chamber of a cylinder, the latter notbeing represented. A camshaft 6′ driven by a crankshaft actuates theinlet valves 3 and 4 that are surrounded by the valve springs 7 and 8with an interposition of a roller-type cam follower 9. The camshaft 6′and the inlet valves 3 and 4 function as a type of variable valvecontrol. For this purpose, the camshaft 6′ is equipped with asleeve-type sliding cam device 10 that is located on the camshaft 6′axially mobile in the direction A-A, but is connected torsion-resistantwith the latter whereby the sliding cam device 10 functions with theinterposition of a positive hub connection 11 that is a multiple grooveprofile or a serration profile (See FIG. 3).

The sliding cam device 10 is equipped with three cam paths 12, 13 and 14with different cam forms Ni, Nii and Niii that lie next to each otherand are combined in a cam block 15. The cam block 15 is bounded by thehoisting curves 16 and 17 on both sides. The actuation elements 22, 23,24, and 25 having control pins 18, 19, 20 and 21 are used for theadjusting the sliding cam device 10 on the camshaft 6 (which could, forexample, be of an electromagnetic or hydraulic type) that are locatedradially to the sliding cam device 10. Depending on the circuitry of oneof the cam paths 12, 13 or 14, the control pins 18, 19, 20 or 21 areengaged with the hoisting curves 16 and 17 that can be formed, forexample as U-shaped recesses 26 and 27 as in FIG. 2.

The hoisting curves 16 and 17 of the sliding cam device 10 carrying thecam paths 12, 13 and 14 show different hoisting curve sections Hks forthe engaged control pins 18, 19, 20 and 21. The hoisting curb sectionsHks of the hoisting curves 16 and 17 are formed according to the outercircumferences of the sliding cam device shown in FIGS. 4 and 5 and areconnected through the inlet section 28, a first centering section 29, anadjustment section 30 and a second centering section 31 to the outletsection 32. An area of the cutouts 26 and 27 for the control pins 18,19, 20 and 21 between the start of the inlet section 28 and the end ofthe second centering 31 is designated with AfdS as shown in FIG. 5. Theinlet section 28 tapers off in the direction of the first centeringstation 29 like the funnel 33. A first adjustment section 34 is locatedupstream from the funnel 33. In addition, a locking section 35 and asecond adjustment section 36 are located downstream from the secondcentering section 21. A locking device 37 serves for the correctpositional arrangement of the cam paths 12, 13 and 14 in relation to theinlet valves 3 and 4 as seen in FIG. 2 comprising three radial grooves39, 40 and 41 at the inner circumference plane 38 of the sliding camdevice, whereby the camshaft 6′ is equipped with a cylindrical recess 42for a locking ball 43 and a spiral spring 44 in the area of the grooves39, 40 and 41.

It can be seen from FIG. 2 that ring elements are provided on both sidesof the cam block 15 in the form of a cam hub 45 carrying the cam paths12, 13 and 14, which protrude from the cam block 15. The hoisting curves16 and 17 are located in the ring elements 46 and 47. Radial webs 48 and49 of the ring elements 46 and 47 border on the cam paths 12, 13 and 14of the cam block 15. The ring elements 46 and 47 and the cam hub 45 aremade in one piece. Finally, it is also conceivable that the ringelements 46 and 47 and the cam hub can consist of several parts.

After starting the internal combustion engine 1, one of the cam paths12, 13 or 14 will actuate the roller-type cam follower 9 and with it theinlet valves 3 and 4. Depending on the parameter or the revolution drivepedal position or such of the internal combustion engine 1, the variablevalve control is actuated, meaning the actuation elements 22, 23, 24 or25 are activated and one of the control pins 18, 19, 20 or 21 engageswith the cutouts 26 or 27, which leads to an axial movement of thesliding cam device in the direction A-A based on the adjustment section30 and to a defined switch of one of the cam paths 12, 13 or 14.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. A valve drive for an internal combustion engine comprising: acamshaft, and a sliding cam device equipped with cam paths lying next toeach other with different cam forms and hoisting curves which functiontogether with actuation elements equipped with control pins foradjustment of the sliding cam device, wherein at least one of thehoisting curves of the sliding cam device equipped with the cam paths isequipped with different hoisting curve sections for an engaged controlpin of a corresponding actuation element.
 2. The valve drive accordingto claim 1, wherein the hoisting curve sections of the at least one ofthe hoisting curves are formed by an inlet section, a first centeringsection, an adjustment section and a second centering section.
 3. Thevalve drive according to claim 2, wherein an outlet section is attachedto the second centering section.
 4. The valve drive according to claim2, wherein the inlet section tapers off in the direction of the firstcentering section in the form of a funnel.
 5. The valve drive accordingto claim 1, wherein the sliding cam device has a cam block forming a camhub carrying the cam paths on both sides and equipped with ring elementsas a type of a hollow body that protrude over the cam block.
 6. Thevalve drive according to claim 5, wherein the ring elements are equippedwith the hoisting curves.
 7. The valve drive according to claim 5,wherein the ring elements include radial webs which border on the campaths.
 8. The valve drive according to claim 5, wherein the ringelements and the cam hub consist of one part.
 9. The valve driveaccording to claim 5, wherein the ring elements and the cam hub areassembled from several parts.
 10. The valve drive according to claim 6,wherein the ring elements and the cam hub consist of one part.
 11. Thevalve drive according to claim 7, wherein the ring elements and the camhub consist of one part.
 12. The valve drive according to claim 6,wherein the ring elements and the cam hub are assembled from severalparts.
 13. The valve drive according to claim 7, wherein the ringelements and the cam hub are assembled from several parts.
 14. Aninternal combustion engine comprising: a valve drive having a camshaftand a sliding cam device equipped with cam paths lying next to eachother with different cam forms and hoisting curves, and actuationelements equipped with control pins adapted to function together withthe hoisting curves for adjustment of the sliding cam device, wherein atleast one of the hoisting curves of the sliding cam device equipped withthe cam paths is equipped with different hoisting curve sections for anengaged control pin of a corresponding actuation element.
 15. Theinternal combustion engine according to claim 14, wherein the hoistingcurve sections of the at least one of the hoisting curves are formed byan inlet section, a first centering section, an adjustment section and asecond centering section.
 16. The internal combustion engine accordingto claim 15, wherein an outlet section is attached to the secondcentering section.
 17. The internal combustion engine according to claim15, wherein the inlet section tapers off in the direction of the firstcentering section in the form of a funnel.
 18. The internal combustionengine according to claim 14, wherein the sliding cam device has a camblock forming a cam hub carrying the cam paths on both sides andequipped with ring elements as a type of a hollow body that protrudeover the cam block.
 19. The internal combustion engine according toclaim 18, wherein the ring elements are equipped with the hoistingcurves.
 20. The internal combustion engine according to claim 18,wherein the ring elements include radial webs which border on the campaths.
 21. The internal combustion engine according to claim 18, whereinthe ring elements and the cam hub consist of one part.
 22. The internalcombustion engine according to claim 18, wherein the ring elements andthe cam hub are assembled from several parts.